The shaft collar is a simple, yet important, machine component found in many power transmission applications, most notably motors and gearboxes. The collars are used as mechanical stops, locating components, and bearing faces. The simple design lends itself to easy installation.
O locking collar has a counterbored recess made purposely eccentric to the collar bore. When assembled on the shaft, this eccentric recess engages, or mates, with an eccentric cam end of a bearing's inner ring. … This assembly grips the shaft 
tightly with a positive binding action that increases with use.
Pre-heating is not recommended as collars can lose holding power
Never “tack-weld” collars as damage to the axles heat treat can occur
Sealed bearing insert with eccentric shaft locking collar and grub screws to allow tightening against the shaft once fitted. This insert has a parallel outer diameter and is typically fitted directly into the machine frame
EPT aluminum front subframes are notorious for “walking” or “shifting,” creating clunks, squeaks and groans while turning, starting and/or stopping. VW's repair to this was issued through a TSB (Tech Service Bulletin) whereby a set of shims and larger shank diameter bolts were installed to take up the space between the subframe and the body, limiting subframe motion and tightening the clamp load on the subframe. However, the noise and shifting subframe issue can still return with these shims installed.
If you notice signs of subframe shifting, identified by looking underneath the front suspension and inspecting where the front subframe meets the body and a separation line is observed, or if you hear knocking or clunking while making turns, starting and/or stopping you more than likely will need this ECS Front Subframe Locking Collar Kit.
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